1. Field of the Invention
The present invention relates to a method and catheter for treating biological tissues with light activated drugs, and more particularly, to a method and catheter for treating biological tissues by delivering a light activated drug to a biological tissue and exposing the light activated drug to ultrasound energy.
2. Description of Related Art
It is frequently desirable to kill targeted biological tissues such as tumors and atheroma. One technique for causing targeted tissue death is called photodynamic therapy which requires the use of light activated drugs. Light activated drugs are inactive until exposed to light of particular wavelengths, however, upon exposure to light of the appropriate wavelength activated drugs can exhibit a cytotoxic effect on the tissues where they are localized. It has been postulated that the cytotoxic effect is a result of the formation of singlet oxygen on exposure to light.
Photodynamic therapy begins with the systemic administration of a selected light activated drug to a patient. At first, the drug disperses throughout the body and is taken up by most tissues within the body. After a period of time usually between 3 and 48 hours, the drug clears from most normal tissue and is retained to a greater degree in lipid rich regions such as the liver, kidney, tumor and atheroma. A light source, such as a fiber optic, is then directed to a targeted tissue site which includes the light activated drug. The tissues of the tissue site are then exposed to light from the light source in order to activate any light activated drugs within the tissue site. The activation of the light activated drug causes tissue death within the tissue site.
Several difficulties can be encountered during photodynamic therapy. For instance, since the light activated drug is typically administered systemically, the concentration of the light activated drug within the targeted tissue site is limited by the quantity of light activated drug administered. The concentration of the light activated drug within a tissue site can also be limited by the degree of selective uptake of the light activated drug into the tissue site. Specifically, if the targeted tissue site does not selectively uptake the light activated drug, the concentration of light activated drug within the tissue site can be too low for an effective treatment.
An additional problem associated with photodynamic therapy concerns depth of treatment. Light cannot penetrate deeply into opaque tissues. As a result, the depth that light penetrates most tissue sites is limited. This limited depth can prevent photodynamic therapy from being used to treat tissues which are located deeply in the interior of a tissue site.
There is currently a need for a method and apparatus which can be used to cause death to tissues death deep within a tissue site. When the method and apparatus employ light activated drugs, the method and apparatus should be able to provide an appropriate concentration of light activated drug within the tissue site.
An object for an embodiment of the invention is causing tissue death within a tissue site.
Another object for an embodiment of the present invention is locally delivering a light activated drug to a tissue site and activating the light activated drug.
Yet another object for an embodiment of the present invention is locally delivering a light activated drug to a tissue site and delivering ultrasound energy to the delivered light activated drug to activate the light activated drug.
A further object for an embodiment of the present invention is using a catheter to locally deliver a light activated drug to a tissue site and delivering ultrasound energy from an ultrasound element on the catheter to activate the light activated drug.
Yet a further object for an embodiment of the present invention is including the light activated drug in an emulsion, locally delivering the emulsion to a tissue site and delivering ultrasound energy to the light activated drug within the tissue site to activate the light activated drug.
Even a further object for an embodiment of the present invention is including the light activated drug in a liposome, locally delivering the liposome to a tissue site and delivering ultrasound energy to the light activated drug within the tissue site to activate the light activated drug.
An additional object for an embodiment of the present invention is including the light activated drug in an aqueous solution, locally delivering the aqueous solution to a tissue site and delivering ultrasound energy to the light activated drug within the tissue site to activate the light activated drug.
Yet a further object for an embodiment of the present invention is including the light activated drug in an emulsion, systemically delivering the emulsion, providing the light activated drug sufficient time to localize within a tissue site and delivering ultrasound energy to the light activated drug within the tissue site to activate the light activated drug.
Even a further object for an embodiment of the present invention is including the light activated drug in liposomes, systemically delivering the liposomes, providing the light activated drug sufficient time to localize within a tissue site and delivering ultrasound energy to the light activated drug within the tissue site to activate the light activated drug.
An additional object for an embodiment of the present invention is including the light activated drug in an aqueous solution, systemically delivering the aqueous solution, providing the light activated drug sufficient time to localize within a tissue site and delivering ultrasound energy to the light activated drug within the tissue site to activate the light activated drug.
Another object for an embodiment of the present invention is coupling a site directing molecule to a light activated drug, locally delivering the light activated drug to a tissue site and activating the light activated drug within the tissue site.
Yet another object for an embodiment of the invention is providing a catheter for locally delivering a media including a light activated drug to a tissue site. The catheter including an ultrasound assembly configured to activate the light activated drug within the tissue site.
A further object for an embodiment of the invention is providing a catheter for delivering a media including a light activated drug to a tissue site. The catheter including an ultrasound assembly for reducing exposure of the light activated drug to ultrasound energy until the light activated drug has been delivered from within the catheter.
A kit for causing tissue death within a tissue site is disclosed. The kit includes a media with a light activated drug activatable upon exposure to a particular level of ultrasound energy. The kit also includes a catheter with a lumen coupled with a media delivery port through which the light activated drug can be locally delivered to the tissue site. The ultrasound transducer is configured to transmit the level of ultrasound energy which activates the light activated drug with sufficient power that the ultrasound energy can penetrate the tissue site.
A method for causing tissue death in a subdermal tissue site is also disclosed. The method includes providing a catheter for locally delivering a light activated drug to the subdermal tissue site, the catheter including an ultrasound transducer. The method also includes locally delivering the light activated drug to the tissue site; producing ultrasound energy from the ultrasound transducer, and directing the ultrasound energy to the subdermal tissue site following penetration of the light activated drug into the subdermal tissue site to activate least a portion of the light activated drug within the subdermal tissue site.
A method for activating a light activated drug is also disclosed. The method includes providing a catheter with an ultrasound transducer. The method also includes introducing the light activated drug into a patient""s body where a subdermal tissue site absorbs at least a portion of the light activated drug; producing ultrasound energy; directing the ultrasound energy to the light activated containing subdermal tissue site including the light activated drug; and activating at least a portion of the light activated drug in the subdermal selected tissue site.
A method for releasing a therapeutic from a microbubble is also disclosed. The method includes providing a microbubble with a light activated drug activatable upon exposure to ultrasound energy; and delivering ultrasound energy to the microbubble at a frequency and intensity which activates the light activated drug to cause a rupture of the microbubble.
A microbubble is also disclosed. The microbubble includes a substrate defining a shell of the microbubble and having a thickness permitting hydraulic transport of the microbubble. The microbubble also includes a light activated drug activatable upon exposure to ultrasound energy. Activation of the light activated drug causes a disruption in the shell sufficient to cause a rupture of the microbubble. The microbubble further includes a therapeutic releasable from the microbubble upon rupture of the microbubble and yielding a therapeutic effect upon release from the microbubble.